US regulators may be preparing to place a black box warning — the FDA’s most serious safety alert — on COVID-19 vaccines, according to multiple reports citing individuals familiar with ongoing policy discussions.
The proposal, though not yet finalised, has already triggered significant concern across the biopharmaceutical sector, with industry leaders warning that the move risks undermining one of the most successful vaccination campaigns in modern history.
A boxed warning typically highlights life-threatening risks that must be weighed against a product’s benefits and is reserved for issues such as opioid misuse, Accutane-related birth defects or rare complications linked to smallpox vaccination.
Sources told CNN that the initiative is being led by Dr Vinay Prasad, the newly appointed head of the FDA’s Center for Biologics Evaluation and Research (CBER), who has questioned the risk–benefit profile of COVID-19 vaccines in internal memos.
It remains unclear whether any proposed warning would apply to all COVID-19 vaccines or solely to mRNA-based products from Pfizer/BioNTech and Moderna.
The FDA has also not confirmed whether updated labelling would span all age groups.
Manufacturers categorically dispute the need for such action.
Moderna and Pfizer issued statements in September reaffirming the strong global safety record of Spikevax and Comirnaty, citing continuous regulatory monitoring across more than 90 countries and more than one billion doses delivered.
“No new or undisclosed safety concerns” have been identified, Moderna noted.
Public health experts also argue that current evidence strongly supports vaccine safety and efficacy.
A CDC report published this week found that updated 2024-25 formulations reduced emergency and urgent care visits for COVID-19 by 76% in children aged nine months to four years and by 56% in older children.
Meanwhile, modelling estimates suggest vaccinations prevented nearly 20 million deaths worldwide in their first year of deployment.
The reported proposal has deepened tensions within Washington, where COVID-19 vaccination policies remain politically charged.
Former FDA and CDC officials have publicly criticised the idea in The New England Journal of Medicine, warning that politicised interference could erode confidence in evidence-based regulation.
The Department of Health and Human Services emphasised that no decision has been made, stating: “Unless the FDA announces it, any claim about what it will do is pure speculation.”
For now, industry and global regulators will continue to monitor developments closely as the end-of-year timeline approaches.